The present invention relates to a mechanical coupling for elastic axial and radial constraint with torsional freedom, especially for elastic pivots and suspensions and the like.
The mechanical coupling according to the present invention finds application in, for example, the following sectors (the list that follows is an indication and not exhaustive):
the automotive sector, for
elastic pivots for the connection of the suspension levers of front and/or rear axles;
elastic pivots for connecting the anti-roll bar to the frame;
elastic pivots for leaf-spring/frame connection;
elastic pivot for the connection of the reaction rod of the power train;
farming and earth-moving machinery, for
cabin support;
joint for excavator arm;
rail and tram sector, for
power cardan joints;
steering box links.
Mechanical couplings are known, consisting generally of coaxial metal bushes between which a rubber sleeve is compressed (in effect making a rubber bush). These are used for absorbing torsional, axial and radial deformations.
The main shortcoming of these known couplings is the need to find a xe2x80x9cphysicalxe2x80x9d compromise between deformations in the axial and radial directions, and torsional deformations.
In particular, radial rigidity and torsional rigidity (at least within the range of limited angular amplitude of about xc2x130 degrees max.) are found to be directly proportional to each other and dependent on the amount of rubber inserted between the metal sleeves.
Moreover, axial rigidity is always low and it is impossible to absorb axial and/or torsional overloads.
Taking the above shortcomings as its starting point, the present invention aims to provide a remedy thereto.
GB 2.245.952 discloses an elastic link bearing composed of two identical bearing elements which are placed coaxially opposite one another and each of which is inserted into one of the end faces of a link lug. Two composite tubular member made of metal and elastomer are held in the link lug with a press fit.
The correct operation of the link bearing needs two opposite elastomeric bushes in order to react axially, in opposite directions, to the axial acting forces. The system reacts, substantially, only when the xe2x80x9celastomeric headxe2x80x9d of the said bushes is compressed. Therefore their maximum axial shift cannot be controlled.
Due to the double bearing element, the link bearing permits the rotation of the outer structure in relation to the inner one exclusively if intermediate sleeves contact each other when urged by a great axial load. Furthermore, the relative rotation of the outer structure in relation to the inner one occurs only when an axial load is applied and maintained.
The elastic link bearing, due to its constructive design, does not allow the outer structure to make a 360xc2x0 rotation in relation to the inner one, with a negligible friction at high frequencies.
In the elastic link bearing the torsional freedom depends exclusively on the applied axial load and is hence very scanty.
U.S. Pat. No. 5,069,431 discloses a bush assembly in which the axial forces can be applied in only one direction. Otherwise, if an axial force is applied, for instance, from right to left (with respect to FIG. 1), the bush assembly could be dissembled. From a constructive point of view, the bush assembly has only one axial stop.
The bush assembly prevents liquids and/or dirt from getting inside only by one side protected through a sealing member. Noise due to dirt penetration could therefore arise.
In the bush assembly, radial loads compress the lateral surface of the rotating insert and through the outer insert cause the rotation stop. Radial loads stop torsional freedom and a contact between the outer insert and the inner one may occur.
The mechanical coupling according to the present invention intends to overcome these drawbacks.
It is therefore the principal object of the present invention to provide a mechanical coupling, and in particular an elastic pivot or suspension, that is capable of reacting as an elastic constraint in the axial and radial directions, while yet at the same time presenting no torsional constraint at torque values close to zero (that is, xe2x80x9ctorsional freedomxe2x80x9d) or at any rate negligible in comparison with the forces present.
With this object in view, the present invention provides a mechanical coupling for elastic axial and radial constraint with torsional freedom, especially for elastic pivots and suspensions and the like, whose essential characteristic is the subject of the main claim, which should be regarded as incorporated here in its entirety.
Further advantageous characteristics are described in the dependent claims.
The mechanical coupling according to the invention presents many advantages, which may be summarized in its ability to provide:
great radial rigidity,
great axial rigidity,
very low torsional rigidity,
absorption of axial and/or radial overloads without permanent deformation,
while making the coupling itself independent of physical limits resulting from its construction and/or from the use of conventional constructional materials or processes.